Surface Plasmon Resonance (SPR) biosensor systems that can monitor interactions between molecules, such as biomolecules, in real time are maintaining increasing interest. A representative such biosensor system is the BIACORE® instrumentation sold by GE Healthcare which uses surface plasmon resonance (SPR) for detecting interactions between molecules in a sample and molecular structures immobilized on a sensing surface. As sample is passed over the sensor surface, the progress of binding directly reflects the rate at which the interaction occurs. Injection of sample is followed by a buffer flow during which the detector response reflects the rate of dissociation of the complex on the surface. A typical output from the BIACORE® system is a graph or curve describing the progress of the molecular interaction with time, including an association phase part and a dissociation phase part. This binding curve, which is usually displayed on a computer screen, is often referred to as a “sensorgram”.
As was published by Kretschmann, E., Optics Communications, 26, (1978) 41-44, the problem of slow speed of operation relative to changes in reflectance and the insufficient precision in the resonance angle determination related with SPR procedures based on moveable mechanics, is solved by the use of a fan-shaped beam (equivalent to several beams simultaneously incident upon the sensor surface over a range of angles) and of collection of the reflected beams (over a range of angles) by an array of angularly spaced detectors.
Furthermore, the transparent block described in EP-A1-0 305 109 may take the form of a hemicylinder creating a wedge-shaped beam, giving a line of a small illuminated area on the sensing surface. The hemicylindrical lens has the advantage that it can be used to perform several tests simultaneously on a single sample. To this end, the sensing surface takes the form of a series of sensitive areas (1D array of sensor spots), each comprising a different antibody, with each separate area being monitored by its own detector in a detector array. The cylindrical focusing principle used to produce an identical angular range of light beams along a focused line for SPR of separate surface areas has been published by Benner, R. E. et al. Optics Communications 30 (1979) 145-149, and Swalen, J D et al. Am J. Phys. 48 (1980) 669-672.